Only the latest version of Roboform (7.x) works with Firefox 4. Older versions (6.x and before) do not, and since they are no longer supported I presume they won't ever.

Owners of Roboform version 6.x can upgrade for free or at a reduced cost (depending on when you purchased 6.x)

Let me say I have used firefox forever but occasionally dabble with IE for certain sites.. This really stinks about ff4 and robo6 not working but I have discovered IE9 and robo6 do work together.. Hopefully down the line someone will figure out how to get ff4 and robo6 to play nice together until then we either can use IE9 which firefox loses or try lastpass.. I am doing both..

actually there is a workaround. all credits to swmyp from ru -board

1. Install Roboform 7.2.7
2. Copy folder "c:\Program Files\Siber Systems\AI RoboForm\Firefox\"
3. Unhide and open toolbar in Firefox if hidden. Quit Firefox.
4. Install Roboform 6.10.2 -dont untick option to install adapter for firefox
5. Replace "c:\Program Files\Siber Systems\AI RoboForm\Firefox\" with your copy from 7.2.7 version
6. Do not hide or close the toolbar in Firefox. Else you will have to reinstall.

now u should have working 6.10.2 roboform with latest adapter from 7.2.7

If toolbar didnt appear right away after restart, remove Roboform toolbar extention from add-ons.